nfit-test: Add platform cap support from ACPI 6.2a to test

Adding NFIT platform capabilities sub table in nfit_test simulated ACPI
NFIT table. Only the first NFIT table is added with the capability
sub-table.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>